gram + rods Flashcards
Name your four gram + bacilli?
Bacillus and Clostridium are spore forming Listeria and Corynebacterium are NON spore forming
Which bacterium of your gram + rods is an obligate anaerobe?explain what this means
Clostridium- can only grow in a anerobic culture (will not grow in an oxygen rich environment)
Name the gram + aerobic spore forming rods and its associated disease
Bacillus anthracis- Cutaneous anthrax (most common): active rods release exotoxin that cause skin ulcers like malignant pustules with a black escher Pulmonary anthrax: aka woolsorters disease cause life-threatening pneumonia GI anthrax Bacillus cereus - gastroenteritis
What is so unique about bacillus anthracis?
only non motile bacilli AND it is the only bacterium with a capsule composed of protein (poly - D- glutamic acid) [it has a polypeptide instead of a polysaccharide] - Capsule prevents phagocytosis
Where does Bacillis anthrax live? and how is it transmitted?
Lives on animals, soil and skin (hair) for long periods resistant to drying, heat, and UV bc it forms a spore. Transmitted by contact on skin, can be inhaled or ingested to cause GI problems.
Which exotoxins are released by B. anthracis?
Protective antigen- promotes entry of toxin into phagocytic cells
Adenylate cyclase- increases the cAMP cascade that results in massive edema (edema factor)
Lethal factor- inactives protein kinase
Pt. is a military personnel with high risk exposure to B. anthracis, can bacterium induced disease be prevented? how?
All high risk occupations (military, farmers or workers with goats/cows where diseas is prevalent) should be given a vaccine that contains the protective antigen (PA) to induces adaptive humeral immunity and make antibodies.
Pt presents with painless black vesicles. If this is a result of B. anthracis how would you confirm? And what is the tx?
Do a gram stain smear (purple)
Aerobic culture on blood agar
Conduct a serology: look for increasing indirect hemagglutinating antibody titer in the plasma serum
TX: ciprofloxin (Cipro) PO/IV [Quinolones} or
doxycycline (doryx) PO [tetracycline]
Pt presents with n/v/d. Which bacteria could have caused this?
Bacillus cereus spores found on rice (fried rice) held warm or reheated (not refridgerated) or
by Staph aureus
Which toxins are released by B. Cereus?
Heat labile toxin: produces watery diarrhea similar to the LT from E. Coli lasting 12-24 hours
Emetic toxin (heat stable toxin): has a short incubation period with n/v and limited diarrhea similar to S. aureus lasting 1-6 hours.
What are the unique factors of Listeria
Non spore forming rods: Have a tumbling motion, can grow both intracellularly and extracellularly, and prefers an immunocompromised host
Why can Listeria undergo intracellular growth?
It can escape phagocytosis of macrophages by rapid egress thanks to it’s listeriolysin O virulance factor
Where does Listeria grow?
Animal GI and genital tracts
Plants and soil.
Cold diary products- soft cheese, deli foods, cabbages
unpasteurized dairy products.
How does infection of listeria occur?
Across the placenta from bacteremic mother
Contact during vaginal delivery from an asymptomatic mother
Ingestion of contaminated raw milk or cheese from infected cows and cold deli foods
Pregnant Pt presents with septicemia. What lab test would you do to rule out Listeria? state treatment.
Gram stain: for purple rods
See for tumbling motility at culture of 25 C
Growth in cold temperature (differentiated from other bacteria)
Non-spore forming
Metabolism: Catalase + (can break down 2H2 O2—>2H2O + O2), aerobic
TX:
Ampicillin PO/IM/IV [aminopenicililnas] or sulfanomide Bactrin PO/IV
add gentamicin IM/IV [aminoglycoside] for IC pts
